When ever I replace a fuel filter on a diesel, I try to do it with the engine already warmed up to aid in starting and to ensure that oil is distributed throughout the engine. Hydraulic pressure can't build, so the injector won't open. As the fuel is injected into the cylinder, the fuel pressure drops and the internal spring re-seates the pintel.Īir inside the fuel lines compresses and this is what causes so many performance and no-start problems. When the fuel pressure in the injectors gets above 1400 psi (new injectors typically open at 1700 psi), it overcomes the spring inside the injector and the valve (pintel) rises off its seat allowing the pressurized fuel to spray from the nozzel.
From the transfer pump the fuel is sent to a plunger-type intensifier pump which increases the fuel pressure further and sends it through the shaft and distributor rotor to each individual injector line, depending on shaft position. It does this by pressurizing the fuel in the injector lines. The injection pump hydraulic head not only distributes the fuel to each injector, but also opens the injectors. Excess fuel passes through a bleed into the governer housing where it is used to lubricate and cool the mechanical portion of the injection pump before returning to the fuel tank. The injection pump also contains a transfer pump which increases the fuel pressure inside the hydraulic head to 60-120 PSI. If the engine speed decreases for a given throttle setting, the governor increases the amount of fuel to maintain the desired RPM. The accelerator linkage basically changes the minimum governed engine speed (RPM). The injection pump contains a governor which contols the amount of fuel delivered to the injectors. Fuel is delivered to the injection pump from the tank(s) by a mechanical lift pump. These engines use what is called a hydraulic injection system.
In the case of a glow plug system problem, plugging the block heater in for a couple of hours usually will get the engine warm enough to start.Ī word of caution about ether or starting fluids: a hot glow plug can ignite starting fluid before you have a chance to crank over the engine and will cause internal damage. The most common problems with the old IDI engines is hard/no start or stall after starting, so that will comprise the bulk of the tips section. Vehicle service information can be found at my Service Page, and much of what is posted at my PowerStroke Page can be applied to these engines as well.Ĭlick here if you're looking for IDI Parts. Hopefully the information posted here will be of some use to you. This page is for those of you who own or work on the older Ford/Navistar diesel engines.